1. Field of the Invention
The present invention relates generally to common channel signaling (CCS), and more specifically is directed toward topologies of Signaling System #7 (SS7) networks.
2. Related Art
In conventional common channel signaling networks (e.g., SS7), mated signaling transfer point (STP) pairs provide an interface to the switches of a long distance carrier and the switches of regional bell operating companies (RBOCs)/local exchange companies (LECs). These standard interfaces are used in the transport of integrated services digital network user part (ISUP) and transaction capabilities application part (TCAP) messages.
FIG. 1 illustrates a conventional topology of a SS7 network. This conventional topology includes various connections that are termed A-links, B-links, C-links, and D-links. In this description, A-links are the connections between a switch and an STP, B-links are the connections between STPs of a single carrier, C-links are the connections between individual STPs in a mated pair, and D-links are the connection between a carrier's STP and a foreign STP.
Returning to FIG. 1, SS7 network 100 comprises a plurality of mated STP pairs 102a-102e that are interconnected by a mesh of B-links 116. This mesh network provides increased survivability due to failures in one or more B-links 116. At the originating and terminating ends, survivability is increased by the connection of a single switch to each STP in a mated pair of STPs 102a-102e. For example, a switch 108a, 108b of a long-distance carrier is connected to mated STP pair 102a and 102b, respectively via A-links 118. Similarly, LEC switch 106 is connected to LEC mated STP pair 104 via A-links 112.
Through this topology, the interconnection between LEC switch 106 and long-distance carrier switch 108 via A-links 112 and 118, D-links 114, and B-links 116 is protected against any failure in a single STP in a mated STP pair. Survivability is a critical feature of common channel signaling network 100. However, it is not the only consideration in estimating the value of common channel signaling network 100. Consideration must be given not only to the efficiency of the network in processing messages but also to the ease at which network expansion can occur.
Generally, network expansion can include expansion of existing STPs or the addition of new mated STP pairs. If mated STP pairs are sought to be added, some of the SS7 traffic on existing mated STP pairs 102a-102e require migration to different mated STP pairs. In equalizing the load between mated STP pairs, all of the mated STP pairs could be affected (e.g., updating of each of their existing databases). These provisioning and maintenance actions can detract from the performance of common channel signaling network 100.